Colistin Use in Patients with Chronic Kidney Disease: Are We Underdosing Patients?

Colistin is administered as its inactive prodrug colistimethate (CMS). Selection of an individualized CMS dose for each patient is difficult due to its narrow therapeutic window, especially in patients with chronic kidney disease (CKD). Our aim was to analyze CMS use in patients with CKD. Secondary objectives were to assess the safety and efficacy of CMS in this special population. In this prospective observational cohort study of CMS-treated CKD patients, CKD was defined as the presence of a glomerular filtration rate (GFR) < 60 mL/min/m² for more than 3 months. The administered doses of CMS were compared with those recently published in the literature. Worsened CKD at the end of treatment (EOT) was evaluated with the RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease) criteria. Colistin plasma concentrations (C_ss) were measured using high-performance liquid chromatography. Fifty-nine patients were included. Thirty-six (61.2%) were male. The median age was 76 (45–95) years and baseline GFR was 36.6 ± 13.6. The daily mean CMS dosage used was compared with recently recommended doses (3.36 vs. 6.07; p < 0.001). Mean C_ss was 0.9 (0.2–2.9) mg/L, and C_ss was <2 mg/L in 50 patients (83.3%). Clinical cure was achieved in 43 (72.9%) patients. Worsened renal function at EOT was present in 20 (33.9%) patients and was reversible in 10 (52.6%). The CMS dosages used in this cohort were almost half those currently recommended. The mean achieved C_ss were under the recommended target of 2 mg/dL. Despite this, clinical cure rate was high. In this patient cohort, the incidence of nephrotoxicity was similar to those found in other recent studies performed in the general population and was reversible in 52.6%. These results suggest that CMS is safe and effective in patients with CKD and may encourage physicians to adjust dosage regimens to recent recommendations in order to optimize CMS treatments.

Lacrimal immunoglobulins in rheumatoid arthritis patients with or without Sjögren's syndrome

The aim of the present study was to analyse immunoglobulin G, A, and M levels in tears of patients with rheumatoid arthritis with or without keratoconjunctivitis sicca (KS) which define Sjögren's syndrome (SS). Tears were collected from the lower cul-de-sac by capillarity (100-300 microl). Tear IgG, IgA and IgM levels were determined by radial immunodiffusion. Samples diluted 1:10 were used for IgA and IgG and non-diluted ones for IgM. Fifty-three patients with rheumatoid arthritis and 30 healthy control subjects were studied. In all individuals IgA predominated in tears, IgG levels were low but with a very wide range and IgM was present in very low concentrations. The IgG concentration in tears showed statistically significant differences between the control group and that of rheumatoid arthritis and KS. IgG in tears correlated positively with the rose bengal test (r=0.2848, p<0.05) and negatively with the Schirmer test (r=0.3042, p<0.05). Tear IgG measurement might provide a marker for eye involvement in patients with rheumatoid arthritis and KS which define SS.